Safety control system for oil burners



Oct. 4, 1955 A. JuDsoN 2,719,582

SAFETY CONTROL SYSTEM FOR OIL BURNERS Filed Feb. 24, 1951 United States Patent O SAFETY CONTROL SYSTEM FOR OIL BURNERS Albert Judson, Portland, Oreg., assignor to Iron Fireman Manufacturing Company, Portland, Oreg.

Application February 24, 1951, Serial No. 212,614

2 Claims. (Cl. 158-28) Reference is here made to my previous patent applications in this art, S. N. 100,131 tiled June 20, 1949, on an Oil Burner Primary Safety Control, now Patent No. 2,552,973 granted May 15, 1951, and S. N. 173,616 filed July 13, 1950, on a Safety Timing Switch, now Patent No. 2,610,273, granted September 9, 1952.

While of different form and circuit arrangement this present invention is functionally similar to the system of S. N. 100,131 and the safety timing switch of this present invention is functionally similar to the device of S. N. 173,616.

This invention relates generally to control systems for condition controlling apparatus in which the condition is subject to the operation or non-operation of an electric motor. More particularly the apparatus of this invention comprises the complete mechanism and circuits required for the safe operation of a gun type, pressure atomizing, motor driven, oil burner under the control of a condition responsive switch such as a thermostat in a space to be heated. lt is of course, understood that the oil burner with which the system is used supplies heat to some form ofkheat transfer device such as a warm air furnace and that the heat is conducted to the space to be heated by some heating medium such as the air heated by such a furnace.

It is a primary purpose of the system to start and stop the electric motor which actuates the air and oil supply to an oil burner in response to the requirements of a condition to be controlled by such operation.

A second object is to ignite the air and oil mixture supplied by the burner at each time of beginning a burner operation.

A third object of my system is to stop the operation of the burner in a pre-set time after the beginning of an operation if at the end of said time period the temperatureat a pre-determined location has not increased to indicate that the burner is operating properly.

A fourth object of my system is to stop the operation of the burner during any period of operation if there is a decrease in temperature at said pre-determined location and if the temperature at said pre-determined location does not increase Within a pre-set time after said decrease.

A fifth object of my system is to prevent the burner `from starting automatically after being shut down in accordance with the third and fourth objects above described.

A sixth object is to provide manual means to reset the system for automatic operation.

A seventh object of my invention is to provide a system, functioning as above required, which will be sensitive to the demands made on it but which will be insensitive to other influences.

An eighth object is to provide mechanisms for my system which will be readily adjustably to the requirements of the environment in which they are used.

How these and other objects are attained is explained -in the following description of my system and on reference to the accompanying drawing in which the single "ice figure is a schematic diagram of the mechanical and electrical mechanisms and circuits of the system.

Referring now to the drawings the numeral 10 indicates generally a thermostat in a space to be heated, 12 is an electric motor and 13 the ignition means of a common type of atomizing Oil burner of which many varieties are well known in the art to be adapted to use with the system of my invention. Numerals 14 to 21 indicate fragments of the insulating base member of the stock mounted primary control unit of my system. The primary control unit includes a transformer 30, a stack temperature trend sensitive switch mechanism 40, a relay mechanism 70, a safety timing and manually reset lockout switch 126 and the associated circuits shown. L1 and L2 are conductors from a source of electric energy supply.

Thermostat 10 is shown to include a stationary contact 9 a contact blade 8 actuated by a bimetallie temperature sensitive element '7 having a conductor terminal 6.

Transformer 30 has a primary winding 31 connected across lines L1 and L2 and a secondary winding 32 having terminals 33 and 34.

Stack switch mechanism 40 includes a cam 41 carried on shaft 42 through a slip friction connection, not shown in detail but well known in the art. Shaft 42 is journalled near cam 41 in the insulating base of the control and extends rearwardly from the control base to extend into a space the temperature of which is responsive to the combustion of the oil burner. Bimetallic member 43 is fixed at its inner end to the base of the control and at its outer end to shaft 42 and is adapted to rotate cam 41 in a clockwise direction when the combustion temperature is rising and in a counterclockwise direction when the combustion temperature is falling. Arm 44 of cam 41 adjustably limits the rotation of cam 41 by contact with limit screws 45 and 46 threaded as shown through ears 47 and 4S raised on base fragments 15. Raise 49 formed on cam 41 operates on roller 50 rotatably carried on one end of spring 51 having its other end secured to conducting switch blade 52 hinged through resilient conducting blade 53 to terminal bracket 54 secured to base fragment 16. Switch blade 52 carries armature 55 of permanent magnet 56 secured to base fragment 14 and also carries switch contact 57 cooperating with adjustable stationary contact screw 58 threaded through plate 59 connected to terminal 60 carried on base fragment 14. Adjusting screw 61 threaded in blade 52 adjustably positions roller 50 with respect to blade 52 and together with adjustably positioned contact screw 58 determines the sensitivity of switch 40 to combustion temperature as sensed by bi-metallic member 43. Screws 45 and 46 determine the temperature trend limits within which switch 40 is set to operate or the amount of combustion temperature fluctuation required to operate the switch.

Relay mechanism 70 comprises a pair of switch stems 71 and 72 both guided for vertical motion in base fragment 18 and movable upward by armatures 73 and 74 hinged respectively to electromagnets 75 and 76 when the corresponding relay operating coils 77 and 78 are energized.

Mounted on insulating base fragment 17 are line voltage switch contacts and terminals 79, 80, 81 and 82 together with low voltage contacts 83 and 84 connected by strap 85 to terminal 86.

Mounted on insulating bar 87 carried on stern 71 is low voltage relay contact 88 and line voltage contacts 89 and 91 connected by strap 90.

Mounted on insulating bar 92 carried on stem 72 is low voltage relay contact 93 and line voltage contacts 94 and 95 connected by strap 96.

Spring 97 around stem 71 is confined endwise between base fragment 18 and head 98 on stem 71.

Spring 99 around stem 72 is confined endwise between base fragment 18 and head 100 on stem 72.

Spring 101 around stem 71 is confined endwise between washer 102 stopped by pin 103 through Vstern 71 and bifurcated extension 104 vof 'armature 73 stopped against base fragment 19. Y

Spring 105 around stem 72 is confined endwise between washer 106 stopped by pin 107 through stem 72 and bifurcated extension 108 of armature 74 stopped against base fragment 20. Y l

`'Spring' 109 around latch cylinder 110 guided for left and right hand motion in base fragment 18 is confined between abutment 111 countersunk into base fragment 18 and collar 112 formed on cylinder f110 and kltiases the sloping end Surface of Cylinder against the sloping surface of collar 113 tilted to stem 72. i n I Pin 114 extending through slo't 115 in latch 116 and secured into lcylinder 110 contines compression spring 117 in the bore of cylinder V110 behind latch 116 and biases latch 116 te 'the left 'with tespeet te cylinder 110. y f

1t Should he here ueted that if Aeen 77 ef magnet 7s is energizedb'efore coil 78 of magnet 76 is 'energized arma*- tu're V7.3 will lift switch stern 71 against the downward bias of spring 97 and cause contacts 88, 89 and 91 to close against contacts 84,81 and 82 respectively. Sloping faced 'collar 118 on stem 7.1 will clear latch 116. Spring 101 is 'fer 'the purpose ef `allowing 'armature 73 te attain its' full travel towards magnet 75 even though the travel of stein 71 Ais stopped by the abutment of the moving 'contacts against the 'stationary contacts. p

Again if coil 78 is `energized before 77 is energized, ftuetu'r'e '74 acting through extension los aud 'spring los will lift switch stern 72 against lthe downward bias of spring '99 aud 4cause eeuftae'ts 93, 95 'and 94 te close against contacts 83, 80 'and A79 're'spectil/eiy. In this easethe sloping face of collar 113 coacting with 'the -sloping face of ylinder 110 causes cylinder 110 to Inye t0 the left against the bias of spring 109 carrying with it latch 116 into position over Vcollar 118 on Mstem 71 'to prevent the upward travel of stem 71 even though coil 77 is later energized. l v

And if coil is 77 is energized before coil 78 is energized stem 71 will travel upward before stem 72 travels upward and in this case the coaction of collar y113 and cylinder 110 vwill cause cylinder 110 to move to the left carrying latch 116 with it until the sloping face of latch 11.6 abuts the sloping Aface of collar 118 on stem 71. Further travel of cylinder 1710 tothe left will ca usclat'ch -11'6 to further Acompress spring 117 in the bore of c'ylinderfll.

Now if coilf77 is deenergizedbefore coil is deenergized, spring k97 will cause stern 71 to retract downwardly and the coaction of the 'sloping face oncollar 1718 on the sloping face of latch 116 will move latch to the right against the bias of spring 117A until collar 118 has moved downwardly clear of latch 111-6 whereupon spring 117' will cause latch 116 to move to the left in latching kposition over collar 118 and thereby .prevent stem 71 from again moving upwardly until coil 78 Fis deenergized and spring 99 has returned stern L72 to its `downward position shown in the drawing and cylinder 110 has returned to the right as shown. .K

Safety timing and manually reset lockout rswitch 1.2.0 comprises flexible switch blades 1,21 and 122 carrying respectively switch contacts 12.3 and 124 each ofthe blades being insulated from the other by block 125W and wboth being secured to base fragment 21 by screws 122g. -ach of the bimetallic temperature sensitive blades 1 26 and 127 have one end secured' to base fragment v21 and the other free to move to its equilibrium position under the intiuence of -its ambient temperature. Switch actuator 1:28 has a holein one end through which is `inserted a tang l129 foi-ming a reduced end portion of -hinge stru't 1.30 whose reduced other end forms a tang 131 Ainserted Vthrough a hole 'formed in hinge clip `'132 secured to base fragment 21 as shown. A reduced end portion 133 ot bimetallic blade 127 is inserted through an ear 134 secured to strut 130. The other end of switch actuator 128 normally rests slidably on the free end of bimetallic blade 126. Tension spring 135 hooked at one end to clip 136 formed an actuator 128 and at the other end to clip 137 secured to base fragment 21 biases actuator 128 toward base fragment 21 against the reaction of 'strut 130 at one end and blade 126 at the other end of actuator 128. K

Switch bar 138 guided in base fragment 21 has one reduced end inserted through a hole in actuator 128 and the other reduced end inserted through a hole in switch blade-121. Reset bar 139 .guided in base fragment 21 has its reduced end 140 inserted thru a hole in base fragment 21, through a hole in switch blade 121, and carries a cross pin 141 against which switch blade 121 rests. Due to the leftward bias of resilient switch blade 121 against pin 141, reset bar 130 is urged leftward until stopped by its shoulder 142 contacting base fragment 321. Resilient switch blade 122 has its contact end biased to the right causing contacts 1-23 land I124 to b'e normally in contact. I

As shown in the drawing b'oth bi'metallic blades v126 and 127 are adapted to have their free ends move upward on an increase in temperature and downward on a decrease in 'temperature so that when subjected 'to the 'same temperature changes there will be no change in the relative positions o'f their 'free ends and the free end of actuator 128 ywill hold its relative position with respect to the 'free end of blade 126. But located adjacent blade 12,6r is electric resistance heater 143 which when energized increases the 'temperature of blade 126 over that of blade 127 and 'after a predetermined time of energiza'tion of heater 143 blade 126 Will move out from under the end of actuator 128 and spring 135 will cause the free end of actuator 128 'to move to the left taking with it switch rod 138 whose end 144 `will press against switch blade 122 thus -rnoving switch contact 124 away from switch contact 123.

When 'the circuit through contacts 123 and 124 is thus broken 'it can only be restored after heater 143 has been deenergized for a sutncient time for blade 126 to return approirinlately 'to the temperature of blade 127 at which time the internal stresses of blade 126 will be such that blade 126 will spring back to the position shown in the drawing when actuator 128 is moved to the right by reset bar 139 when manual pres/sure to 'the right is e'xerted on end 140 of bar 139.

From the drawing it 4will be seen 'that the length "of bar '139 from 'the rig-ht hand end to pin 141 is so made relative )to the length of bar 138 from the end 144 to the shoulder 145 4that when actuator 128 'rests against the right hand end of reset bar 139 'contacts 123 'and 124 will always be separated but if reset bar v139 is pressed to the right and acti-later 128 again latches on blade 126, 'as shown, con'- tacts 123 and 124 will close when the manual pressure is removed from reset bar end 140.

l It is se'entherefore that as regards endwise movement 'of actuator 128 bimetallie blade 127 'compensates for 'any ambient temperature movements of blade 126 and that switch `contacts 123 land 124 will b'e v'separated in an 'approximately uniform length of time whenever heater 143 is energized for, 'that length of time. Also if swit'e'h centaets 123 k:tud 124 lare lopened'bythe movement f blade 126 ont from under 'the eud of actuator '1128 `it 'requires i'nalal manipulation of reset bar 139 to return Vthe switch contacts to their closedrposition which can only be done after 'blade 126 has cooled to its position where actuator 128 can be again llatched on blade 126.

To connect up the above explained 'p'a'rts of ni'y system circuits are completed as follows.

The primary transformer winding 31 is connected to service wire L1 and L2 as shown. Terminal 7-9 is connected'to lin'e 1.11. `One side each of the oil 'burner ignition 'tra-nsformerv'IiG and the oil dburner motor -are connected to service wire 1,2. Wire connects the other side ot th'e motor to terminals 80 and 81. Wire 151 connects the other side of the ignition transformer to terminal 82. Wire 160 connects terminal 34 of transformer secondary winding 32 to relay terminal 86 and stack switch terminal 60. Wire 161 connects terminal 33 of transformer secondary winding 32 to thermostat terminal 9. Wire 162 connects thermostat terminal 6 to safety switch blade 122. Wire 163 connects safety switch blade 121 to one side of heater 143 and one side of relay coil 78. Wire 164 connects the other side of relay coil 78 to relay terminals 88 and'93. Wire 165 connects the other side of heater 143 with one side of relay coil 77. Wire 166 connects the other side of relay coil 77 with stack switch terminal clip 54.

The operation of my system is as follows. Referring to the drawing, the mechanism is seen to be in condition where after an operation of the oil burner the space to be heated is up to temperature as indicated by the open circuited thermostat 10, the stack temperature is lowering as indicated by the closed circuit through the stack switch 40, the safety switch 120 is closed and both of the operating coils 77 and 78 of relay mechanism 70 are de-energized. Then if the temperature drops in the space to be heated thermostat blade 8 will close on thermostat stationary contact 9 and acircuit will be established from transformer low voltage terminal 32 through wire 161, thermostat 10, wire 162, safety timing switch blades 121, 122, wire 163, heater 143, wire 165, relay coil 77, wire 166, stack switch 40 and wire 160 to transformer terminal 34. Timing heater 143 and relay coil 77 will be energized in series from transformer 32. Armature 73 of magnet 75 will lift stem 71 and contacts 88, 89 and 91 will be closed on relay contacts 84, 81 and 82 respectively and through contacts 88, 84 relay coil 78 is energized through wires 160 and 163 in parallel with heater 143 and coil 77 in series. Relay armature 74 will close on magnet 76 and stem 72 will rise to close relay contacts 93, 95 and 94 on contacts 83, 80 and 79 respectively. At the same time collar 113 forces latch cylinder 110 to the left causing latch 116 to abut collar 118 on stem 71. The closing of contacts 94 and 95 on contacts 79 and 80 completes the motor circuit of lines L1 and L2 and because contacts 89 and 91 were previously closed on contacts 81 and 82 the ignition transformer circuit of line L1, 150 and L2 is completed. Contacts 83, 93 completed a holding circuit across contacts 84, 88 for relay coil 78. Thus oil and air is supplied to the oil burner and the mixture ignited in the combustion chamber of the furnace. Stack switch 40 being sensitive to combustion temperature rise or fall and adapted to open on a rise in combustion temperature opens thus deenergizing relay coil 77 and heater 143 and relay stem 71 drops causing collar 118 to crowd past latch 116 which moves to the left when clear of collar 118 and precludes any possible return of stem 71 to closed circuit position of its relay contacts until stern 72 has dropped and cylinder 110 has moved to the right taking latch 116 with it to clear collar 118. When the opening of stack switch 40 caused stem 71 to drop, separating contacts 88, 89 and 91 from contacts 84, 81 and 82, the ignition transformer is deenergized but the motor continues to run due to the continued energization of relay coil 78 through holding contacts 83, 93.

Should the stack temperature have failed to rise sufficently to open stack switch 40 within the preset timing period of about 90 seconds required for heater 143 to influence blade 126 to move out from under timing switch actuator 128 timing switch blades 121 and 122 will be separated and the system shut down completely. But if stack switch 40 opens to indicate that the fire was ignited and progressing normally as above described the burner will continue to operate to supply heat to the space until thermostat 10 is satisfied and contacts 8 and 9 are separated to deenergize relay coil 78 and shut down the motor.

If while the burner is operating anything should happen such as to shut off the supply of oil or air to the burner, stack `switch 40 would be influenced by a falling combustion temperature to close and re-energize coil 77 and attempt to move stem 71 upward to again energize the ignition transformer. This might be dangerous because under these conditions there would probably be an explosive mixture of air and oil vapor in the combustion chamber. It is to prevent such a re-ignition under dangerous conditions that the mechanism of latch and associated parts is provided. As previously described if stem 71 is dropped while stem 72 is in its upward position stem 71 will be prevented from moving upward again by latch 110. In the present case with stack switch 40 closed and contacts 84, 88 open heater 143 is energized by the full voltage of transformer 30 limited only by the reactance of coil 77. Since armature 73 can not close on magnet 75 because stem 71 is latched in its downward position the reactance of coil 77 will be less than when the burner is starting normally with coil 77 energized. Because of the lesser reactance of coil 77 in this case heater 143 will quickly infiuence bimetal blade 126 to shut down the burner by opening the safety timing switch contacts 123, 124.

After being shut down by the safety timing switch as above described it is necessary to reset the timing switch manually before the burner will start again. This necessity allows ample time for the draft through the furnace to purge the combustion chamber so that the burner may start safely.

Having thus declared the purpose of my invention, described a preferred form of mechanism to practice my invention, and explained its operation, I claim 1. In a control system for an oil burner adapted to burn fuel in a combustion space for supply of heat to a space to be heated, said system including an electric driving motor for said burner and electric means for igniting said fuel in said combustion space: the combination of a combustion temperature responsive hot open electric switch; a space temperature responsive electric switch; a safety timing electric switch; an electric heater adapted to cause said safety timing switch to open; a first electromagnetically operated relay; a first operating coil for said first relay; a second electromagnetically operated relay; a second operating coil for said second relay; said first relay including a first power switch and a first control switch; said second relay including a second power switch and a second control switch; a source of electric power; a first circuit including said power source, said ignition means, said first power switch, and said second power switch; a second circuit including said power source, said motor, and said second power switch; a third circuit including said power source, said space temperature responsive switch, said safety timing switch, said electric heater, said first operating coil, and said combustion temperature responsive switch; a fourth circuit including said source of power, said space temperature responsive switch, said safety timing switch, said second operating coil, and said first control switch; said first control switch being connected in parallel with said second control switch; and latch means adapted to permit the closing operation of said first relay if said second relay is in its position of deenergization of said second operating coil but to prevent the closing operation of said first relay if said second relay is in its position of energization of said second operating coil.

2. In combination with a first temperature responsive electric switch, a second temperature responsive electric switch, a first electric relay having a first operating coil requiring energization for operation of said first relay, and a second electric relay having a second operating coil requiring energization for operation of said second relay, means adapted on closure of said first temperature responsive switch when said second temperature responsive switch is closed to energize said first operating coil to operate said first relay, means adapted on the operation of said first relay to energize said second operating 

